Platinum-cobalt catalyst bed for flameless catalytic heater

ABSTRACT

A catalyst bed unit employing measured amounts of cobalt in conjunction with platinum forms the fuel reactive catalyst of the unit to render the heater with which the unit is associated capable of operation at low carbon monoxide emission levels. The catalyst is applied to the support therefor by dissolving chloroplatanic acid and cobalt nitrate in a solution of methanol and water, spraying the mixture onto the support, and heating the unit to reduce the chloroplatanic acid and cobalt nitrate to platinum and cobalt metals.

United States Patent [1 1 Kweller 5] Apr. 9, 1974 {75] Inventor: Esher R. Kweller, Independence,

Kans.

[73] Assignee: Bruest Industries, Inc.,

Independence, Kans.

[22] Filed: Sept. 7, 1972 [21] Appl. No.: 287,069

[52] U.S. Cl. 252/472, 252/466 B, 252/477 R [51] Int. Cl B01j 11/12, 801 11/22 [58] Field of Search 252/477 R, 466 B, 472

[56] References Cited UNITED STATES PATENTS 3,189,563 6/1965 Hauel 252/477 R 3,485,230 12/1969 Harrington et a] 252/477 R 3,589,853 6/]97] Guasco 252/477 R 3,697,447 10/1972 Bettinardi ..252/477R Primary Examiner-Daniel E. Wyman Assistant Examinew W. J. Shine Attorney, Agent, or FirmSchmidt, Johnson, Hovey & Williams 5 7 ABSTRACT A catalyst bed unit employing measured amounts of cobalt in conjunction with platinum forms the fuel reactive catalyst of the unit to render the heater with which the unit is associated capable of operation at low carbon monoxide emission levels. The catalyst is applied to the support therefor by dissolving chloroplatanic acid and cobalt nitrate in a solution of methanol and water, spraying the mixture onto the support, and heating the unit to reduce the chloroplatanic acid and cobalt nitrate to platinum and cobalt metals.

2 Claims, 3 Drawing Figures PLATINUM-=C'OBALT CATALYST BED FOR FLAMELESS CATALYTIC HEATER This invention relates to the field of flameless catalytic heaters and, more particularly, to portable, nonvented, catalytic heaters which are designed for use in tents, camping trailers and other enclosures having only limited circulation of fresh air.

With the upsurge of recreational outdoor camping in recent years, the demand for portable heating units which require no electricity and are flameless when in use has steadily increased. This demand has been met by units which use a hydrocarbon fuel such as bottled propane in conjunction with a precious metal catalyst which reacts with the hydrocarbon fuel at a temperature substantially below its ignition temperature to oxidize the fuel and thereby generate heat. The heater may thus be safely used in the presence of flammable materials such as often found in tents, sleeping bags, and other camping equipment.

The vast majority of such heaters have used platinum as the precious metal catalyst, and while they have performed well from a heat generated standpoint, their use must be limited to open areas in which a freely circulating flow of fresh air exists, inasmuch as carbon monoxide is often emitted as a result of incomplete combustion. The completeness of combustion can be controlled to a certain extent by carefully regulating the rate of fuel inflow so that the catalyst is not overgassed by feeding more fuel thereto than it can handle; however, this procedure may not be practical since decreasing the amount of fuel flow-in this manner also diminishes the heat generated by the heater to the end that it may be unable to maintain a comfortable temperature within the enclosure.

Other attempts at lowering CO emission have included varying the loading of platinum to arrive at a satisfactory emission level, but these have been largely unsuccessful because increasing or decreasing the amount of platinum has only minimal effects in reducing the amount of CO emission.

The present invention relates to the discovery that by adding a predetermined amount of cobalt metal to the platinum, the oxidation of fuel is promoted to such an extent that CO emission is drastically reduced. Quite unexpectedly, however, it has further been discovered that CO emission is not reduced for all loading values of cobalt, but instead, begins to increase when more cobalt is added beyond a strategic amount.

Moreover, it has been discovered that the addition of cobalt to the platinum catalyst has a definite effect upon start-up time, which is defined as that length of time necessary to initiate a self-sustaining, catalytic oxidation of the fuel as it is presented to the combination platinum-cobalt catalyst. Generally speaking, beyond that strategic amount of cobalt which results in the minimum amount of CO being emitted, the length of time which an outside heat source must be applied to the catalyst before it will reach a self-sustaining condition increases sharply as additional cobalt is added. Manifestly, for the sake of convenience, the startup time should be minimized, since in most instances the outside heat source applied to the catalyst in the form of a lighted match moved along an edge of the catalyst unit to ignite the fuel and maintain a flame until the catalyst is capable of reacting with the fuel on its own.

In view of the above considerations, one important object of the present invention is to provide a catalyst bed unit for non-vented, portable catalytic heaters which is capable of reacting with a hydrocarbon fuel presented thereto to generate heat without emitting an excessive amount of carbon monoxide so that the heater may be safely utilized in closed areas such as tents, camping trailers and like enclosures.

A further important object of the instant invention is to provide a catalytic bed unit as above set forth having low CO emission properties which does not render the heater unduly difficult or time-consuming to place in a condition in which the catalytic, heat generating reaction is self-sustaining.

Another important object of the instant invention is to provide a method of making a low CO, platinumcobalt, catalyst bed having the characteristics above set forth.

In the drawing:

FIG. 1 is a front perspective view of a catalyst bed unit embodying the principles of the present invention;

FIG. 2 is a graph showing cobalt loading on the catalyst support versus CO emission and start-up" time; and

FIG. 3 is a graph showing platinum loading on the catalyst support versus levels of CO emission averaged over a selected range of cobalt loading.

The catalyst bed unit 10 shown in FIG. 1 includes a support 12 which is illustrated as being a fibrous mat type, consisting of about 51.7 percent M 0 approximately 47.6 percent SiO 0.15 percent B 0 0.01-0.12 percent Fe O 0.30 percent Na O, and 0.30.5 percent trace organic material. lt is to be understood, however, that the principles of the present invention apply to solid, non-fibrous supports as well and that the fibrous mat is shown only as an example of one form which support 12 may assume. The support 12 may be of any size and shape necessary to conform to the configurations of the housing or plenum chamber in which the mat is normally disposed during use, but has been illustrated as generally rectangular in configuration having a pair of oppositely facing, front and rear surfaces 14 and 16 respectively. The support 12 is normally disposed across the flow of fuel so that the rear surface 16 receives the gas flow and passes it through the support 12 to issue from front surface 14.

The front surface 14 provides the area upon which the catalyst 18 consisting of platinum and cobalt metal is deposited for catalytic reaction with fuel presented thereto. The deposits of platinum and cobalt metal on surface 14 are applied by first preparing a solution of chloroplatinic acid and cobalt nitrate dissolved in water and methanol. The solution is then sprayed onto surface 14 and the support 12 heated to within a range of 600 to 1,000 degrees Fahrenheit to reduce the chloroplatinic acid and cobalt nitrate to platinum and cobalt metals which remain as deposits.

.lt has been discovered that the use of methanol in conjunction with water greatly accelerates the reduction process while eliminating the disadvantages associated with other such agents. For example, formic acid has been used, but this agent is extremely active and has been found to cause the platinum and cobalt metals to precipitate out of solution while disposed in a container prior to being applied to support 12. This action does not result as rapidly when methanol is .used in solution with water where ,the solution ranges from 10 percent to 90 percent methanol.

FIG. 2 graphically illustrates the dramatic effect on C emission of adding cobalt in varying amounts to the platinum on the surface 14. The amount of carbon monoxide emitted is measured in terms of parts of CO per million parts combustion products (corrected for oxygen dilution and unreacted fuel), and the cobalt loading or concentration is measured in terms of grams of cobalt per square foot of surface areas to which it is applied, in this instance front surface 14.

It is to be noted that the curve thus generated by varying the cobalt loading from zero to approximately six grams per square foot is based upon a preferred and constant amount of platinum in a concentration of approximately 0.180 grams per square foot, the determination of 0.l80 grams as a preferred amount being hereinafter described. A similar curve showing the drastic reduction in CO emission through the addition of cobalt to the platinum will result for any chosen platinum loading above or below the preferred amount hereinabove set forth.

As clearly shown, the amount of CO emitted decreases sharply as cobalt loading is increased progressively to within the range from approximately 0.04 grams to 0.15 grams. Because of this drastic increase in CO emission as cobalt loading is increased, it might be expected that the addition of further cobalt would result in a further decrease in CO emission. Quite unexpectedly, however, this is not the case as CO emission begins to increase again as cobalt loading is increased above the 0.15 grams per square foot level. Continued loading of cobalt through the 2, and 6 grams per square foot levels results in a continued rise in CO emissions.

From a standpoint of CO emission, a preferred range of cobalt loading is thus established by the knee on the curve which is defined between 0.004 and 2.0 grams of cobalt per square foot. However, CO emission alone cannot be the sole determining factor in selecting a cobalt loading range since it was discovered that beyond a certain point, cobalt added to the platinum metal has a depressing effect upon the ease with which a self'sustaining catalytic reaction could be initiated. This is also graphically shown in FIG. 2 wherein the start-up time in seconds is plotted against cobalt loading in grams per square foot.

Start-up time maybe defined as that period of time for which an external heat source such as a flame must be applied to the catalyst in the presence of the fuel being combusted in order to initiate a self-sustaining catalytic oxidation reaction. It is to be realized that inasmuch as this type of catalyst bed unit is designed primarily for use in portable camping heaters and the like wherein the external heat source will most often consist of a lighted match, the startup time is especially important from a convenience stand-point. Manifestly, a heater which is excessively difficult and time consuming to start up will not be as successful commercially as one which requires excessive effort to place it in full condition for operation.

FIG. 2 shows that start-up time remains fairly constant at approximately 26 to 27 seconds for all ranges 5 of cobalt loading to approximately 0.45 grams per square foot, whereupon further cobalt loading results in a steady increase in start-up time. The start-up time at a cobalt loading of approximately 2 grams per square foot is approximately 90 seconds, which defines the outer, acceptable limit of start-up time. Thus, the range of 0.004 to 2.00 grams of cobalt per square foot of surface area is presented with idealconditions obtaining when cobalt loading is within the range of 0.04 to 0.15 grams per square foot of surface area.

FIG. 3 illustrates the basis for the selection of approximately 0.180 grams per square foot as the preferred value for platinum loading. The curve represents a plot of the average CO emission level over a given range of cobalt loading for varying platinum loading, showing that CO emission is lowest for any cobalt value when platinum loading is approximately 0.180 grams per square foot of support surface area.

From the foregoing it should be apparent that combining cobalt with platinum on the catalyst support in the manner and amounts described furnishes a bed unit which is capable not only of generating more than adequate heat to maintain a comfortable environment within which to-sleep, work, or play, but also a safe, substantially CO-free environment by virtue of the completeness of combustion which is effected. Moreover, the present platinum-cobalt catalyst is not limited to use with propane, but is also well suited for other hydrocarbon fuels such as butane and methane. In addition, fuel gases containing hydrogen have been successfully utilized in conjunction with the catalyst.

Having thus described the invention, what is claimed as new and desired to secure by Letters Patent is:

1. For use in a flameless, radiant heat catalytic heater utilizing a gas fuel, a catalyst bed unit capable of catalytically reacting with the fuel to generate heat without excessive CO emission, said unit comprising:

a catalyst support having a catalyst-carrying surface;

a deposit of platinum metal on said surface in an amount capable of providing a self-sustaining oxidizing reaction with the fuel as it flows into proximal relationship with the platinum at said surface; and

a deposit of cobalt metal associated with the platinum deposit on said surface in an amount ranging from approximately 0.04 to 0.15 grams per square foot of said surface to promote combustion of the fuel to such an extent that the emission of CO is minimized.

2. A catalyst bed unit as claimed in claim 1, wherein said deposit of platinum is approximately 0.180 grams per square foot of said surface. 

2. A catalyst bed unit as claimed in claim 1, wherein said deposit of platinum is approximately 0.180 grams per square foot of said surface. 